There is an obvious gap between Ruyer’s early “pan-mechanism”, developed in the Esquisse d’une philosophie de la structure (1930), and the panpsychism one finds in his mature work. We will see that working within the field of the former gave Ruyer the occasion to find what he identified to be the “great natural way of philosophy”. This consists of searching in humans the trace of the mode of being common to all the psycho-biological individualities. Ruyer’s affiliation to this “great way” has never failed, which means that one can say his early “pan-mechanism”, which Ruyer quickly abandoned, was fruitful, at least from a methodological point of view.